BuddyPress.org

Put it all in one column:

/* Aligns Registration Profile Details fields to the left */
#buddypress .standard-form #basic-details-section,
#buddypress .standard-form #blog-details-section,
#buddypress .standard-form #profile-details-section {
    width: 100%;
}
#profile-details-section {
    margin-top: 20px;
}

And the finish button too (recommended):

#buddypress .standard-form#signup_form div.submit {
    float: left!important;
    margin: -12px 3px 3px 3px!important;
}

That should line it all up in 1 row. Congrats on not paying someone $1000 for that info 🙂